1. Field of the Invention
The present invention relates to a repositionable self-expanding intravascular aneurysm cover device and a hydraulic deployment system for placing the device at a preselected location within a vessel of the human body, and more particularly, relates to a device and hydraulic deployment system for the device which may be used to initially place the aneurysm cover device at a first location within a vessel and if it is desirable to reposition the device, the device may be withdrawn into the deployment system and subsequently repositioned at a different location.
2. Description of the Prior Art
For many years flexible catheters have been used to place various devices within the vessels of the human body. Such devices include dilatation balloons, stents, embolic coils and aneurysm covers. Examples of such catheter devices are disclosed in U.S. Pat. No. 5,108,407, entitled, “A Method And Apparatus For Placement Of An Embolic Coil”; U.S. Pat. No. 5,122,136, entitled, “Endovascular Electrolytically Detachable Guidewire Tip For The Electroformation Of Thrombus In Arteries, Veins, Aneurysms, Vascular Malformations And Arteriovenous Fistulas.” These patents disclose devices for delivering an embolic coil to a preselected position within a vessel of the human body in order to treat aneurysms, or alternatively, to occlude the blood vessel at the particular location.
Devices, such as stents, which are placed in vessels may take the form of helically wound wire, or tubular like structures, with numerous patterns defining the walls. Examples of various stent configurations are disclosed in U.S. Pat. No. 4,512,338, entitled, “Process For Restoring Patentcy To Body Vessels”; U.S. Pat. No. 5,551,954, entitled, “Biodegradable Drug Delivery Vascular Stent”; and U.S. Pat. No. 4,994,071, entitled, “Bifurcating Stent Apparatus And Method.” Stents are generally formed of materials which retain their shape under the pulsatile flow conditions encountered when placed within the body vessel. Some materials that have been used to make such stents include metals and alloys, such as, stainless steel, tantalum, tungsten and nitinol, as well as polymers such as polyvinyl alcohol (PVA), polyglycolic acid (PGA) and collagen. On occasion multiple stents are placed at a given location to provide the desired vascular support.
In the past, the deployment of stents has been accomplished by numerous techniques. One such technique used to deploy a typical wire stent uses a pusher wire to push the wire stent through the lumen of a properly positioned cannula. As the stent exits the cannula it takes a predetermined shape until completely deposited in the vessel. This procedure is usually conducted under fluoroscopic visualization, such that the movement of the stent through the vasculature can be monitored. With these placements systems there is very little control over the exact placement of the stent since the stent may be ejected to a position some distance beyond the end of the cannula. As is apparent, with these latter systems, when the stent has been released from the cannula it is difficult, if not impossible, to retrieve the stent or to reposition the stent.
Numerous procedures have been developed to enable more accurate positioning of stents within a vessel. One such procedure utilizes a helically wound wire loop stent with a relaxed diameter. The stent is wound on a smaller diameter delivery while fixing the ends of the stent. This keeps the stent in a small diameter, tightly wound coil. This system is then delivered through the lumen of a properly positioned catheter exiting at a desired location. Once the delivery wire is activated to release the ends of the stent, the stent radially expands to its relaxed larger diameter. Such a stent positioning method is disclosed in U.S. Pat. No. 5,772,668, entitled, “Apparatus For Placing An Endoprosthesis.”
Another stent positioning system utilizes a self-expanding tubular stent. This stent has a relaxed diameter that approximates the diameter of the vessel to be supported. For transport through the catheter, the stent is positioned on a smaller diameter delivery wire. A sheath is positioned over the stent/delivery wire assembly constraining the stent to a smaller diameter. Once the assembly is placed at the desired location in the vasculature, the sheath is withdrawn exposing the stent allowing the stent to return to its predetermined larger size. The expansion of the stent uncouples the stent from the delivery wire while depositing the stent in the vessel at the desired location.
Still another stent positioning system utilizes a hydraulic stent deployment system for placing a self-expandable stent into the vessels of the body, and in particular into the small vessels of the brain. More particularly, this stent positioning system utilizes a catheter having a distal tip for retaining the stent in order to transport the stent to a predetermined position within a vessel and a control mechanism for releasing the stent at the preselected position. The control mechanism generally takes the form of a pressure generating device, such as a syringe, which is used to apply pressure to the catheter to thereby cause the distal end of the catheter to expand radially which in turn causes the stent to be released from the distal tip of the catheter. An example of such a stent positioning system is illustrated in U.S. Pat. No. 6,254,612, entitled, “Hydraulic Stent Deployment Systems,” and assigned to the same assignee as the present invention.
An example of a self-expanding tubular stent is illustrated in U.S. Pat. No. 6,267,783, entitled, “Stent Which Is Easily Recaptured And Repositioned Within The Body.” This self-expanding stent is formed by cutting and removing diamond shaped sections from the wall of a thin-walled nitinol tube to thereby form a relatively flexible, skeletal, tubular stent. The stent may be compressed to a smaller size for insertion into a vessel and then may be permitted to expand to a size where the stent contacts the walls of a vessel. The disclosed stent may also be recaptured and repositioned within a vessel.
An example of a self-expanding aneurysm cover is shown in U.S. Pat. No. 5,591,195 entitled, “Apparatus And Method For Engrafting A Blood Vessel.” The aneurysm cover illustrated in this patent is comprised of an expandable wire frame, which upon expansion, supports a fabric material which covers the mouth of an aneurysm.